


Illicit Affairs

by heartsocold



Category: Shadowhunters (TV)
Genre: Alternate Universe - Canon Divergence, Alternate Universe - Soulmates, Angst with a Happy Ending, Based on a Taylor Swift Song, M/M, no beta we die like men
Language: English
Status: Completed
Published: 2020-08-24
Updated: 2020-08-24
Packaged: 2021-03-06 15:47:00
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,327
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26081404
Author URL: https://archiveofourown.org/users/heartsocold/pseuds/heartsocold
Summary: Everything that people said about the love they had for their soulmate - Alec felt it with Magnus.And Magnus loved him back. Magnus was the best thing that had happened to him.But he wasn’t Alec’s soulmate. Nephilim loved once and Alec knows that Magnus is his person but he isn’t his soulmate.Or: The one where they're not soulmates but they love each other and it's all one big mess.
Relationships: Alec Lightwood/Andrew Underhill, Magnus Bane & Ragnor Fell, Magnus Bane/Alec Lightwood
Comments: 8
Kudos: 79





	Illicit Affairs

**Author's Note:**

> I blame Taylor Swift for this.

Alec looks at the man wrapped in his arms, fast asleep and he can’t help but think about how much he hates the concept of soulmates. 

He didn’t always hate it. As a matter of fact, the idea of someone out there being his perfect match was something that he had fantasized over for most of his life. The knowledge that there was someone who would love him wholeheartedly for all that he was - flaws included - had pulled him through some of his darkest days.

Soulmates were quite common for everyone Mundane, Nephilim and Downworlders alike although the concept meant different things for the factions. 

Shadowhunters saw the world in varying shades of black and white until they met their soulmate. It was said that once you met your soulmate, your world would be filled with a multitude of colors at once, all at full brightness. Alec remembers everyone telling him how amazingly indescribable the moment would feel, their words causing him to feel a pang of sadness.

He had met his soulmate, Andrew Underhill, approximately four years ago. He had recently turned twenty and had finally taken over as the Head of the New York Institute. Andrew had been assigned as the Head of Security by the Clave and the first thing that Alec had noticed was how tall he was. He was at eye level with Alec - being only one inch shorter - so the second they shook hands, Alec saw his eyes change from grey to a muted blue. He blinked in surprise, noting that the man had short, curly, blond hair. Blond. Blue. Colors that weren’t grey. This man was his soulmate. 

Alec recalls the way he had felt in that moment. He had been giddy with anticipation. He had been ecstatic and his heart had been pounding in his chest but there hadn’t been any of the sparks he had expected to fly when they had met. Naturally, they had started dating. It was fun. Alec liked having a partner to run the institute with but that’s all it felt like. 

They’ve been together for four years and Alec trusts him. He cares about him. He even loves him - but not in the way that he should. The love he has for Andrew doesn’t feel romantic. It’s not the burning passion he thought he’d feel. Instead, the love he feels is familial. It’s the fondness he feels for his siblings. It’s the warmth he feels in his chest when he sees Aline - with whom he’s grown up with. It’s nothing like what everyone else describes. It’s nothing like what he’s dreamt of.

It’s nothing like what he feels for Magnus. 

He had met Magnus almost a year ago, around the time Jace had met his soulmate - Clary. She was a nephilim who had spent her entire life unaware of the ShadowWorld. Like everything else to do with Jace, Clary had brought nothing but trouble with her. Her mundane best friend - Izzy’s soulmate - had even managed to get himself kidnapped and turned into a vampire. It had been a rough few months but Magnus Bane - one of the most powerful warlocks in the World - had agreed to help them.

Alec had helped him take down a Circle member and the moment he had seen Magnus, his heart skipped a beat. He was the most beautiful man Alec had ever laid his eyes on. Andrew was attractive but Alec had never thought he was anything special. Magnus on the other hand had struck him as downright ethereal. He was otherworldly and then he had spoken - a bad meat pun - but his voice had sent chills running through Alec.

Alec was attracted to him in a way he had never experienced before. He had thought other men were sexy but they were nothing compared to Magnus. As the High Warlock of Brooklyn, Magnus and Alec crossed paths often after that first time since the Downwold and the Nephilm had decided to work together to win the battle that was coming. 

After that, it had become clear that the attraction Alec felt was mutual and while he tried not to act on it, him and Magnus bonded on an intimate level. There hadn’t been anything physical at first but the more they interacted, the deeper their bond grew. Soon enough, Alec had been telling him things he had never dared say aloud, even to Andrew or his parabatai. Magnus in turn, shared secrets he had held to himself for over eight hundred years. 

Eventually, after a battle where they nearly lost their lives - and one that left them both traumatised - they had lost what little control they had and kissed. It was one of the best moments of Alec’s life. The spark that he had always anticipated, the raw burning desire and passion that he craved - he felt it with Magnus. Magnus made him weak with a simple look. He craved his touch. His smile was something that never failed to make Alec happy. His laughter was Alec’s favorite sound. Everything that people said about the love they had for their soulmate - Alec felt it with Magnus.

And Magnus loved him back. Magnus saw him for who he was. He didn’t look at him and see the Head of the Institute. He didn’t see one of the Clave’s best warriors. He saw _ Alec _ . He held him when the world was too much. His arms made Alec feel safe. He could show all his flaws and his fears and be loved for them and not in spite of them. Magnus was the best thing that had happened to him. 

But he wasn’t Alec’s soulmate. Nephilim loved once and Alec knows that Magnus is his person but he isn’t his soulmate. He was going to be twenty-five soon and he was expected to be married by then. The Clave had rigid views about the relationships of Shadowhunters - it didn’t matter what you felt or how unhealthy the relationship was, you were to wed your soulmate. Raziel doesn’t make mistakes. That meant he would have to propose to Andrew soon but every time he thought about it there was a constriction in his chest that made it hard to breathe. 

His arms tightened around Magnus. He didn’t want to think about the day where he wouldn’t have this. The loft had become their safe haven. Magnus was his happiness. He swallowed roughly as he thought about that being ripped away from him.

“What are you thinking about?” Magnus’ voice pierced his thoughts and he looked down to see the older man peering at him through bleary eyes and poorly concealed concern.

“Go back to sleep,” Alec whispers, pressing a kiss on the crown of his love’s head.

“I can’t do that,” Magnus says, pressing himself closer to Alec. He shifts so that he’s practically on top of Alec, their limbs entangled beneath the silk sheets covering them. Alec sinks into the mattress and Magnus cradles his face, kissing him softly. “What’s bothering you?”

Alec smiles weakly, memorizing Magnus’ features and the look of absolute love in his unglamoured eyes.

“I-I can’t stop thinking about how much it’ll hurt when I have to give this up,” His voice is rough with the attempt to hold back his tears. 

“Oh, Alexander,” Magnus’ face crumples. There isn’t anything he can say to make this better. Their time is limited and they both know it. He wants to yell and rave at how unfair the Clave is. He wants to kidnap Alec and run away with him. He wants to spend the rest of their lives holding Alec but he can’t. 

“I love you,” He proclaims instead, joining their lips once again. “We have now, okay? Let’s live for that, yeah?”

Alec nods, gripping Magnus tight enough to leave a bruise but it doesn’t feel like enough. He wants to hold him until they’re one entity. He never wants to leave but he knows they’re on borrowed time. They always have been but Magnus is right. He’s not twenty-five for another few months. They still have time.

-

“Alec? Are you listening?” Alec’s head shoots up from his phone, his fingers automatically locking it before someone can see he’s texting Magnus and his eyes land on Andrew watching him.

“Yeah, sorry. What were you saying?”

“I was asking if we’re still on for dinner tonight. I’ll meet you on the rooftop at seven?” Alec wants to scream ‘no.’ He wants to run to Brooklyn and spend the night on Magnus’ balcony, wrapped in his love’s arms even as the sun rises over the horizon but instead he smiles and nods affirmatively.

Andrew smiles back at him happily and comes over to press a kiss onto Alec’s lips. Alec forces himself to kiss him back like he’s supposed to even as a sick feeling settles in his stomach in protest.

They pull back and Andrew looks at him, searching his face for something that he won’t find. Alec had spent years crafting a mask to wear and Andrew never learnt to read the emotions beneath it. 

“Are you okay Alec?” 

“Yeah, I’m just tired. You know the usual.”

Andrew sighs heavily but doesn’t say anything. Instead, he kisses Alec again chastely and then he's on his way. Alec swipes at his lips then resumes his work. He doesn’t know how he’s supposed to spend the rest of his life like this when he’s disgusted by his soulmate’s touch. 

The hours pass too quickly for Alec’s liking and before he knows it, he’s dressed in one of his better suits - all black - and on his way to the rooftop. He pushes open the door and his breath gets caught in his throat when he sees the rose petals on the table and the numerous candles lighting the area. 

No. No, no, no, no, no, no- 

This can’t be happening. Shadowhunters don’t spend months engaged. If they get engaged tonight, he’ll be married within three days. 

Fuck. He can’t breathe. He needs to leave. He needs to get out of here - he’ll tell Andrew that something came up and Jace needed help on a patrol or that Izzy -

“You’re speechless, huh?” Andrew’s hand is resting on the small of his back and his body in tense, buzzing with nerves. He feels like he’s about to throw up.

“I-”

“I know this isn’t exactly your style but I wanted to do something special. I figured you’d appreciate something lowkey though.”

He turns to face Andrew and he’s grinning, looking at Alec the way soulmates are supposed to. Alec knows he doesn’t look at him like that. Alec doesn’t know what to say. He’s scared that if he speaks he’ll start crying. They were supposed to have a few months left. 

Andrew takes his left hand and sinks to his knees, his free hand producing a small box which reveals a thick gold band with a combination of the wedded union rune and the love rune carved into it. 

“Alec Lightwood, you are my soulmate. You’re a strong, fearless leader who inspires me every single day. You’ve made me want to be the best version of myself. You’re everything in a man I’ve ever wanted. Will you marry me?”

Alec can’t speak past the lump in his throat. He can’t think past the roaring in his ears. His body goes into auto-pilot and he feels himself nod as he bites his lower lip hard enough to draw blood in an attempt to hold back his tears.

Andrew must read it as a good sign because he slips the gold band onto Alec’s ring finger then jumps up to hug him. He wraps his arms around Alec’s neck and squeezes him for a moment before pulling back to connect their lips.

“Alec?” He asks in worry, pulling back from the kiss. “Is that blood? Are you okay?”

“I-I-,” Alec stutters. “I have to go.”

He roughly pulls himself out of Andrew’s grip and rushes through the door. He pulls out his stele once he's out of the institute and activates his speed rune, heading towards the one place he’s known as home.

-

Magnus feels the change in his wards that let him know Alec’s here and he flicks his hand, allowing the doors to open for Alec before he’s even standing in front of them.

He’s pouring himself a glass of wine, waiting for Alec to make his way up the stairs when his voice comes from behind, rough and raw and broken in a way that lets him know Alec is in pain.

“Magnus,” He says and Magnus drops both the bottle of red wine and the glass in his hands as he turns to find Alec. He’s sweating and his face is flushed, one tear leaking out as Magnus’ gaze lands on him. He looks fragile and Magnus feels his own heart break. He opens his arms and Alec falls into him, his body going pliant as sobs wrack through him, loud and painful.

They sink to the floor and Magnus rocks them back and forth, whispering sweet nothings into his air and his hands rub up and down his back. Alec clutches onto him tighter than he ever has before, crying until he starts to hyperventilate and Magnus starts to worry.

“Alexander, sweetheart, you have to calm down okay? Please, baby, try to take deep breaths, yeah? Follow my breathing, yes, that’s it. You’re okay. I’m here,” He coaxes and slowly Alec begins to calm down. 

They stay on the floor, Alec encased by Magnus’ arms as his crying finally stops and he’s able to catch his breath. Magnus wipes the tears from his puffy face, placing a kiss on his forehead. Alec kisses him and Magnus is taken aback by the pure emotion in the kiss. His own heart stutters because he has a bad idea as to why Alec is acting like this. The kiss is filled with love and longing - like it’s the last time they’ll get to do it.

Eventually the need for oxygen becomes too strong and they pull apart, resting their forehead against each other. 

Alec brings his hand up to trace the skin near Magnus’ eyes but his gaze gets caught on the glint of the gold band on his finger and he rips it off, throwing it across the room. He presses his face into Magnus’ neck as he breathes heavily and Magnus’ grip grows stronger, the sound of the ring rolling before it finally settles filling the room.

“Andrew...proposed?” Magnus asks slowly, his fears being confirmed. Alec nods, closing his eyes as his knuckles clench, his nails digging painfully into his palms. Magnus slips his hand into Alec’s to stop him and they both hold on for dear life. 

“How much time do we have?” Magnus questions after a few minutes, his voice soft and defeated, laced with the pain they both feel.

“I’ll be married within three days,” Alec croaks out. Magnus kisses him again, roughly this time.

“You should go,” He grits out when he pulls away, ripping himself away from Alec and turning his back to him. He knows they have to end this. They have no choice. He can’t continue having an affair, not when it’s with a married man. Not when Alec’s bound officially by Clave laws. Adultery would land them both in the Gard. 

Alec’s hand reaches out and grabs Magnus’ wrist. 

“Not yet,” He begs. “Stay with me. Please. Just for tonight. I’ll go tomorrow.”

Magnus closes his eyes to fight back the onslaught of tears and nods. He’ll hold the love of his long life in his arms for one last time tonight.

“When the sun comes up, it’ll be over,” Magnus declares, turning to look at his heartbroken Shadowhunter. 

“I know,” Alec agrees. “Tonight, I need you to make love to me. One last time.”

-

“Alec, what’s going on buddy? Underhill said you two got engaged then ran out?” Jace asks, his hand hovering over his parabatai rune. 

Jace has spent the entire night feeling an influx of emotions from Alec and the only thing that had stopped him from going to him was the knowledge that he had been with Magnus. Now that Alec was back at the Institute and didn’t have anything that required his immediate attention, him and Izzy had decided to lock themselves in his office in an attempt to find out what was going on since Alec seemed to be in even more pain now than he had the night before. 

“It’s over.”

Those are the only two words Alec says but when he looks up at them, they both know what he’s talking about. He’s pale and his eyes are bloodshot, the skin under them bruised and puffy. Izzy walks over to where he’s sitting and lowers herself onto his lap. He wraps his arms around his sister’s waist and she tucks his head against her chest, her fingers tangling themselves in the strands as she tries to comfort him.

They both know what Magnus means to him. Jace had confronted him about it one night because he had never felt Alec so happy. At first he thought his brother had managed to work out things with his soulmate but then he realized that the bouts of happiness came when Alec was away from the Institute. Alec had confessed everything to him whereas Alec had gone to Izzy the very first time he realized how deep his feelings for Magnus ran. They both wanted nothing more than for their brother to be happy so they helped Alec sneak around with the warlock who loved him the way he deserved to be loved.

The way Underhill didn’t.

“Are you going to go through with the wedding? It isn’t too late to call it off,” Isabelle ventures.

“Have you ever heard of a Shadowhunter calling off a wedding to be with someone who isn’t their soulmate? Mom would have my head,” Alec scoffs.

“So be the first. And if Maryse has a problem with you choosing your happiness, she can deal with me,” Jace grits out angrily.

“Jace is right. We’re behind you, Alec. One hundred percent. We just want you to be happy.”

Alec sends them both a sad smile. “I wish it were that easy. I have a duty to fulfill though. To this Institute, to our family. I have to marry him.”

They both want to argue more. Alec can see it in their faces but Izzy looks to Jace who gives her a slight shake of his head and Alec knows they won’t argue more for his sake. Instead, Jace comes round and pulls them both into a hug.

“We’re here for you, Alec. Whatever you need.”

And right now, the only thing he needs is for them to hold him up throughout the next few days.

-

When Magnus wakes, the space next to him is empty. 

He reaches a hand out, his fingers tracing the empty spot where Alec should be reverently. It doesn’t feel right without him. The crimson red of his sheets looks like a murky brown to him. He feels as though his entire life has become devoid of color since he lost Alec. He squeezes his eyes shut at the pain in his chest and he hears something shatter outside, his magic acting out in place of his emotions. There’s a knock on his door that he tries to ignore but the person is insistent. He pulls himself out of bed but no one is there when he rips open the door. Instead he finds an envelope. 

_ ‘You are cordially invited to the wedding of Alexander Lightwood and Andrew Underhill.’ _

He gets dressed and portals himself to Ragnor since Catarina is at work.

Ragnor simply raises an eyebrow at Magnus’ entrance, taking a sip of his tea as he continues reading his book.

Magnus makes himself comfortable, spreading out on Ragnor’s couch like one would at a therapist’s.

“Is there something I can help you with or have you come here to mope?” Ragnor grouches after a considerable amount of time has passed.

“Do you remember what I’ve told you about Alexander?”

“The Shadowhunter you’ve deemed as the love of your immortal life? Of course I remember him.” 

“Our time together is up and now I feel as though there’s a void in me. Everything seems to be losing color. It’s like every bit of happiness I’ve ever known has been taken away from me.”

Ragnor shuts his book, giving all his attention to his friend.

“What do you mean losing color?”

“I know it seems dramatic but I swear to you Ragnor, it seems as though everything is...muted - for lack of a better word. I can’t explain it.”

“Magnus, did Alec die?” Ragnor’s tone is grave and Magnus sits up.

“No! He’s getting married. To his soulmate.”

Ragnore frowns. “I know that a lot of downworlders, warlocks specifically, don’t take soulmates as seriously as the Clave does but how much do you know about it exactly?”

“I don’t understand what you’re asking me.”

“Magnus, I know you think that because you still see in color even though Etta died you always will but that’s not true. Etta was your first soulmate and she was the reason you saw color but some warlocks often have more than one soulmate, especially if their soulmates are mortal. Warlocks typically only lose sight of color when they lose their final soulmate, the true love of their life. Obviously, this doesn’t happen often so it’s not quite heard of but there are records that prove this to be true. It’s exceedingly rare that Warlocks are matched to Nephilim but I would say that losing them to marriage would count, since they take runes and runic magic is quite bonding, not to mention powerful.”

Magnus freezes as his mind struggles to comprehend what Ragnor is saying.

“You think that Alexander is the true love of my life and that makes him my soulmate? That’s why I’m seeing this with less color?”

“Yes! That’s exactly what I’m saying.”

“But, even if that were true for me, Alec already has a soulmate and he isn’t a Warlock,” Magnus points out, wiping his sweaty hands on his pants. 

“Contrary to popular belief, Raziel does make mistakes. There have been records of a few mismatched soulmates and some cases where they have two soulmates or even none at all.”

“You’re saying that Alexander and I might just be soulmates after all?”

“Magnus, compared to yesterday, does the colors you see simply look muted or are they fading?”

Magnus closes his eyes and tries to focus. After Alec had walked out the door, his world seemed to have become muted but now that he’s thinking about it, it seems to become more and more muted as time passes.

“I’m losing the sight of color. It’s fading. That means…”

Ragnor smiles at him. “I think you have a wedding to be at. You’ve wasted enough time.”

-

“It is time for Alec Lightwood and Andrew Underhill to mark each other with the wedded union rune. A rune on the hand and a rune on the heart, a union is born.” 

Andrew takes the golden stele and is about to draw the rune on Alec’s wrist when Alec’s vision is flooded with color. It’s all so bright and Alec’s breath catches as he realizes this is how he’s been seeing all along. He didn’t realize but for the past few days the colors had faded. These are the colors he’s seen since he met…

“Magnus,” Alec whispers in realization and then the sound of a door slamming resonates throughout the room. 

“Alec?” Andrew questions and Alec snatches his wrist back, turning just in time to see Magnus strut down the aisle. He’s dressed in a dark, velvet burgundy jacket with a black button up underneath to match his pants and shoes. His hair is spiked in a mohawk, the tips dyed to match his jacket, a small piece of hair dropping into his face. His eyes are lined with dark kohl and his eyes stare into Alec’s very soul. 

His jaw is clenched and he stands still, waiting for Alec to do something. Maryse gets up to say something to Magnus but he cuts her off without even looking at her, his eyes still on Alec.

“Maryse, this is between me and your son. I’ll leave if he asks me too.”

Magnus is here. If Alec turns him away, it’ll destroy him. They both know that. Alec also knows that he’s bound by duty to marry his soulmate. And Andrew is his soulmate. He’s the reason Alec’s world went from a greyscale to color. But then, if that were true, why does he see colors the brightest when Magnus is around? 

Alec has questions but right now they don’t matter because Magnus - Magnus is his  _ person _ . He’s the love of his life. He’s his happiness. He’s everything that Alec has been waiting for his entire life - soulmate or not. 

He turns to Andrew. If he goes through with this, he’s condemning them all to a lifetime of unhappiness.

“I’m sorry. I thought this was the right thing to do but it’s not.”

“Alec-” Andrew tries to protest. He reaches out to grab him but he’s met with air because Alec is already striding down the aisle to Magnus, his eyes set in determination.

“Alec-” His mother tries to intervene but he twists out of her grasp.

“Enough,” He demands, finally crossing the last few steps to Magnus. He reaches out and takes the lapels of Magnus’ jacket into his hands, pressing their lips together, fueled by the force with which he loves him. 

“We’re soulmates,” Magnus whispers when they pull apart, his hands coming up to hold onto Alec’s waist.

“I know,” Alec says and they’re kissing again. 


End file.
